Absorbent articles intended for body fluid management typically are comprised of a top sheet, an ADL (acquisition distribution layer), a back sheet, an absorbent core located between the ADL and back sheet, and an optional surge layer located below the top sheet/ADL and over the absorbent core. The surge layer is mainly comprised of cross-linked cellulosic fibers. A surge layer composed of cross-linked fibers usually provides better transfer and distribution of liquid, increases rate of liquid absorption, reduces gel blocking, and improves surface dryness.
Methods of making cross-linked fiber are described in several patents like U.S. Pat. Nos. 4,204,054; 3,844,880; 3,700,549; 3,241,553; 3,224,926; 7,074,301; and 7,288,167; European Patent No. 0,427,361 B1; and European Patent No. 1,745, 175 A4, the disclosures of which are incorporated by reference herein in their entirety.
Crosslinking is usually carried out at a temperature of over 160° C. Exposing pulp to such high temperature causes yellowing. Another major issue is that the cross-linking is carried at low pH using an acidic crosslinking agent with pH of about 2.5. So, produced fibers have highly acidic properties (very low pH), due to residual unreacted carboxyl groups present on crosslinking agent. Fiber with very low pH may cause skin irritation when used in absorbent article intended for body waste management.
It is therefore, an object of the present invention to provide a crosslinking agent for making fiber with modified functionality and process of making the fiber at milder temperature and near neutral pH. The fiber is suitable for use as a liquid transfer in absorbent articles intended for body waste management.
Another goal of the present invention is to make such transfer pulp free from the before-mentioned disadvantages such as yellowing, low pH and high content of knots and fines.